Table 1.

Study Population and Clinical Characteristics by Race/Ethnicity

Variable	Categories	Total		NHW		AA		HW		P1
		N	%	N	%	N	%	N	%
Total		375		58	15	78	21	239	64
Age (yrs)	<50	96	26	18	31	20	26	58	24	0.746
	50–59	150	40	22	38	34	44	94	39
	≥60	129	34	18	31	24	31	87	37
	Mean (SD)	56.0 (9.0)		55.6 (9.1)		55.3 (9.3)		56.4 (9.0)
BMI (kg/m2)	<25	97	26	29	50	12	15	56	23	<0.0001
	25–29.99	126	34	15	26	18	23	93	39
	≥30	152	40	14	24	48	62	90	38
	Mean (SD)	29.4 (6.5)		26.9 (6.6)		32.7 (8.3)		28.9 (5.3)
Smoking status	Never	246	66	36	62	55	71	155	65	0.391
	Former	109	29	21	36	18	23	70	29
	Current	20	5	1	2	5	6	14	6
# Comorbidities2	0	150	40	28	48	20	26	102	43	0.068
	1	139	37	19	33	34	43	86	36
	2	63	17	7	12	20	26	36	15
	≥3	23	6	4	7	4	5	15	6
Diabetes	No	332	88	55	95	61	78	216	90	0.004
	Yes	43	12	3	5	17	22	23	10
Hypertension	No	214	57	40	69	31	40	143	60	0.001
	Yes	161	43	18	31	47	60	96	40
Thyroid disease	No	336	90	50	86	74	95	212	89	0.197
	Yes	39	10	8	14	4	5	27	11
Tumor stage	0	76	20	7	12	15	19	54	29	0.001
	IA–B	186	50	38	65	30	38	118	49
	IIA–B	91	24	12	21	31	40	48	20
	IIIA–C	22	6	1	2	2	3	19	8
ER	Positive	291	78	44	76	53	68	194	81	0.049
	Negative	84	22	14	24	25	32	45	19
HER2	Positive	32	12	3	7	7	12	22	13	0.458
	Negative	282	88	51	93	59	88	172	87
Triple negative	No	304	85	47	85	56	73	201	89	0.002
	Yes	54	15	8	15	21	27	25	11
Axillary surgery	None/SLNB	250	67	39	67	57	73	154	64	0.370
	ALND	125	33	19	33	21	27	85	36
Chemotherapy	None	200	53	32	55	42	54	126	53	0.885
	Taxane	166	44	25	43	33	42	108	45
	Other	9	3	1	2	3	4	5	2
Hormone Therapy/Initiation time	None/after RT	181	48	37	64	44	56	100	41	0.027
	AI before RT	102	27	9	16	16	21	77	32
	AI during RT	14	4	3	5	2	3	9	4
	Tamoxifen before RT	65	17	6	10	12	15	47	20
	Tamoxifen during RT	13	4	3	5	4	5	6	3
RT type	Conventional	308	82	45	77	66	85	197	82	0.753
	Hypofractionation	58	16	12	21	9	11	37	16
	Partial3	9	2	1	2	3	4	5	2
Total RT dose (Gy)	<60	116	31	22	38	22	28	72	30	0.433
	≥60	259	69	36	62	56	72	167	70
	Mean(SD)	57.7 (5.6)		58.0 (5.2)		57.9 (6.3)		57.6 (5.5)
Boost	Yes	331	88	55	95	66	85	210	88	0.178
	No	44	12	3	5	12	15	29	12
Breast volume (cc)	< 892.1(MD)	182	49	37	64	21	27	124	52	<0.001
	≥ 892.1	189	51	21	36	56	73	112	48
	Mean(SD)	996 (517)		816 (481)		1224 (641)		965 (454)
V105 (cc)4	<241.7 (MD)	167	50.2	33	60	35	50	99	48	0.262
	≥241.7	166	49.8	22	40	35	50	109	52
	Mean(SD)	313 (288)		304 (318)		331 (298)		310 (276)

¹P values from chi-square test or Fisher’s exact test excluding missing.

²Sum of 11 patient-reported comorbidity conditions: diabetes, hypertension, heart disease, lung disease, thyroid disease, cirrhosis liver, stroke, chronic bronchitis, hepatitis, tuberculosis, and other.

³The nine patients with partial breast irradiation were excluded from all subsequent analyses since they received only 1 week of RT.

⁴V105 (cc): Breast volume receiving > 105% of prescribed dose. SD: standard deviation, MD: median.